Stability and Change

In this modeling exercise, students model how pre-domesticated plants and animals have been changed through selective breeding in order to explore the cross-cutting concept “Stability and Change”.

This modeling exercise leverages the phenomena of artificial selection to have students explore how selective breeding can either cause a stabilization of traits or change based on human choice. The initial introduction to the phenomena can be done a number of different ways but should include a contrast between a plant or animal before and after selective breeding (sometimes closest living relatives need to be used here for a historical comparison). Often students will automatically assume that life (plants and animals) have been relatively stable throughout Earth’s history. So, for example, you could show how the fruits and vegetables they eat would have existed a couple of thousand years ago. It is important to have students reflect on this contrast between current domesticated plants and animals and those that historically existed. This brings up the larger question as to how they have changed and leads to the modeling exercise. This can be done as either individual modeling or done as a whole class and just requires that students have numerous small pieces of paper (3”X3”) of paper and something to model with. You start with a picture of a pre-domesticated plant or animal (corn is a great one!). Have each student draw that pre-domesticated plant or animal as accurately as they can. This simulates genetic variation in the ancestral population. Collect all of these samples and put them on the board (or on a doc cam) for students to look at and ask them which variations they would choose to allow to reproduce if they wanted the next generation to provide more food or another resource. Once the class has decided they then draw this second picture. Complete a few more rounds of this process and each chosen picture tends to look more like the domesticated version. Once the modeling is completed students can take time to reflect on how artificial selection occurs and the ways that humans can impact stability and change in other species through selective breeding. NOTE: We do not recommend this modeling exercise for natural selection as it tends to promote non-science ideas involving intelligent design, which is not endorsed by the scientific discipline.

Suggested Modeling Elements: N/A or Review Library. This modeling exercise suggests a general usage of drawing, predicting, and observations in learning stability and change within an ecosystem. For teachers interested in customizing this exercise further into students' modeling-making, we encourage you to explore the visual library tool and choose the modeling elements/moves that best fit your instructional plan, if applicable.

Suggested Sensemaking Components: Movement/Motion, Zoom in/out, Flow of Matter